Decondenser unit

ABSTRACT

To counteract condense dew on a transparent cover film ( 3 ) covering each well ( 2 ) in an array of wells which forms a test plate ( 1 ) having a lower side formed by the bottoms of the wells ( 2 ) and an upper side formed by the upper edges of the wells ( 2 ) onto which edges the cover film ( 3 ) is sealingly attached, the test plate ( 1 ) is for a set time placed with its lower surface contacting a cooling plate ( 5 ), which is by a cooling element ( 8 ) kept at a set temperature below the room temperature, and with its upper surface in a distance from a heating plate ( 4 ) which is by a heating element ( 7 ) kept at a set temperature higher than the room temperature.  
     A control box ( 9 ), which receives feed back signals from the cooling plate ( 5 ) and the heating plate ( 4 ), controls the power supply of the heating and cooling elements ( 7, 8 ) to maintain the temperatures for the heating and the cooling plates ( 4, 5 ) set by temperature setting buttons ( 13  and  14 ).

[0001] Method and apparatus for counteracting condense dew on a transparent cover film covering each well in an array of wells which forms a test plate having a lower side formed by the bottoms of the wells and an upper side defined by the upper edges of the wells onto which edges the cover film is sealingly attached.

[0002] In modern laboratories high numbers of chemical compounds are currently examined for different properties, which makes them useful for different purposes, especially for therapeutic uses. For the examination is used test plates comprising a large number of juxtaposed wells. In each well a compound to be examined is placed together with a reagent, which react with the compound if this compound has the wanted properties. The reagent are chosen so that the reaction can be visually inspected, although this visual inspection is mostly made by a camera which photographs the content of the wells and produces images which can later be inspected by a human or a machine to select the wells containing useful compounds. In fact the visual inspection is performed by sensors receiving a light signal from the content of the well which signal may be immediately evaluated to decide whether the content of the inspected well is interesting or not.

[0003] When compounds and reagent are filled in all the wells a transparent cover film covering the wells and closing them hermetically is glued to the surface formed by the upper edges of the wells. This cover film prevents evaporation of the liquid in the wells and prevents contamination of the content of the wells. Further it prevents contamination of the inspection apparatus if the plate is tilted sufficiently to make the liquid flow over the edges of the wells.

[0004] Unfortunately it has appeared that water is inclined to condense on the side of the film facing the wells as an array of small dew pearls which makes the film over the wells appear mat and makes the visual inspection impossible. Even when this inspection is performed totally automatically the reading is substantially impaired when condensation on the cower film occurs Experiments have shown that a condensation with small droplets on the lower side of the cover film results in a 12% reduction of the read signal whereas larger droplets may cause a loss of 30-40% of the signal. If the extent of condense varies from well to well, the interpretation of the signals will be ambiguous. Blowing hot air over the film for a while may make the condense water evaporate to make the film transparent but the effect will only last for a time which is too short to allow the wanted inspection of the wells. If too hot air is blown over the film for more than just a while, the content of the wells or the well itself or its cover film may be damaged before an inspection can be completed. An alternating heating and inspection makes the inspection process slow and cumbersome and is unsuited for an automatic scanning process.

[0005] An objective of the invention therefore is to provide a method by which condense water on a transparent cover film can be prevented, removed and kept away for a while sufficient to perform an automatized inspection of all the wells on a test plate before disturbing dew formations occur.

[0006] This is obtained by method for counteracting condense dew on a transparent cover film covering each well in an array of wells which forms a test plate having a lower side formed by the bottoms of the wells and an upper side formed by the upper edges of the wells onto which edges the cover film is sealingly attached, which method according to the invention is characterised in that the test plate for a set time is placed with its lower surface contacting a cooling plate which is kept at a set temperature below the room temperature and with its upper surface in a distance from a heating plate kept at a set temperature higher than the room temperature.

[0007] Appropriately the cooling plate is maintained in the temperature interval 0-10° C. and the heating plate is held in the temperature interval 50-110° C. preferably in the interval 60-75° C. whereby temperatures, which may harm the samples in the wells, the wells or their cover film, or the gluing between well edge and film, are avoided. The time the test plate stays between the cooling plate and the heating plate may be 1-10 minutes which has appeared to keep the covering film free from harmful condense for 30 minutes which is sufficient for a careful optical reading of the reactions in the individual wells.

[0008] The invention further relates to an apparatus by which the method can be performed. Such an apparatus is characterise in that it comprises,

[0009] a cooling plate on which a test plate can be placed,

[0010] a heating plate parallel with the cooling plate in a distance from the cooling plate which distance is larger than the thickness of the testplate,

[0011] cooling means maintaining the cooling plate at a set temperature lower than the room temperature, and

[0012] heating means maintaining the heating plate at a set temperature over the room temperature.

[0013] According to the invention the heating means may appropriately comprise an electric resistive heating element and a heat distributing plate to obtain an even heating all over the heating surface facing the upper side of the test plate.

[0014] The cooling plate may be cooled by a Peltier element, which provides solid state cooling without use of moving parts or flowing liquid.

[0015] The apparatus may be provided with means for setting the temperatures of the heating and the cooling plates, which means cooperating with feed back signals from the cooling and the heating plates controls a power supply so that a set temperature for the respective plates is maintained at a set value. Hereby the heating and the cooling are provided in a reproducible way.

[0016] The cooling plate is shaped with a raised platform mating a depression in the bottom of the test plate. This way a safe positioning of the plate on the cooling element is obtained and the matching platform and depression ensure a good heat conductance between the cooling plate and the test plate. The depression is found in common used test plates as it further serves the purpose of making the test plates suited for piling.

[0017] The space between the heating plate and the cooling plate may be ventilated to avoid dew on the cooling plate as any liquid on the outer side of the covered test plate is unwanted by the succeeding handling of the test plates.

[0018] In the following the invention is explained in further details with references to the drawing, wherein

[0019]FIG. 1 shows a photography of a test plate with condense on the film covering the wells of the test plate,

[0020]FIG. 2 shows a photography of a test plate without condense on the film covering the wells of the test plate,

[0021]FIG. 3 shows schematically a sectional side view of an apparatus according to the invention with a test plate positioned in said apparatus,

[0022]FIG. 4 shows schematically and end side view of an apparatus according to the invention, and

[0023]FIG. 5 shows schematically a front side view of the apparatus shown in FIG. 4.

[0024]FIG. 1 shows a test plate comprising an array of wells wherein samples are placed and inspected through a transparent film covering the wells to protect their content against contamination and drying out and further ensuring that the content of the wells are not spilt if the plate is tilted during the handling. As the wells containing a liquid is hermetically closed by the cover film which is glued to the edges of the partitions between the wells, the air between the samples and the cover film will be saturated with vapour which will condense on the cover film as small droplets which reflects the light and makes the inspection window appear as a white matt surface so that no precise visual inspection can be made. The condensed droplets make the covered open end of the wells appear as white fields in FIG. 1.

[0025]FIG. 2 shows a test plate as the one shown in FIG. 2 but seen before liquid has condensed on the cover film. In this picture the film over the wells remains transparent so that the well can be looked into. This makes the areas over the wells appear as black. The white markings in FIG. 2 originate from reflections in the upper edges of the partitions, which separate the wells.

[0026] To avoid condensation on the film the temperature of this film must be raised over the dew point for the vapour in the well. This may be obtained by blowing hot air over the plate and the cover film. However, the heat capacity of the film is rather low so its temperature quickly returns to the dew point when the test plate is removed from the heating station and inserted in the inspection apparatus.

[0027] In an apparatus according to the invention and which is schematically shown in FIG. 3 not only the temperature of the film is raised, but further the temperature of the bottoms of the wells and of the samples are lowered to lie below the dew point for the vapour over the sample so that condensation rather takes place at the bottom of the well than at the cover film. When a sufficient temperature difference is provided it will last some time before condensation on the film takes place, which time is sufficient to perform the wanted inspection of the content of each well.

[0028]FIG. 3 shows schematically an apparatus for treating a test plate in advance of inspection of the wells. The test plate 1 has an array of wells 2 which are covered by a cover film 3, which adheres to the edges of the wells and seals each of the wells 1.

[0029] The apparatus comprises a heating plate 4 in or on the upper side of which an electric resistance heating element 7 is installed, and a cooling plate 5 which is cooled by a Peltier element 8 mounted with its cool side in contact with the cooling plate, whereas its warm side is provided with not shown cooling ribs. The cooling plate 5 is provided with a raised platform 6 with oblique edges, which platform 6 mates a depression in the bottom of the test plate so that this test plate is secured against horizontal movements on the cooling plate 5.

[0030] A control box 9 has a power input line 10 and contains a controlling circuit controlling the power supply through a line 11 to the heating element 7 and through a line 12 to the cooling element 8 on the basis of temperature signals from the heating plate 4 and from the cooling plate 5 through lines 15 and 16, respectively, and of the settings of a pair of temperature setting buttons 13 and 14 for the heating plate and the cooling plate, respectively. As a further controlling feature the distance between the cooling plate and the heating plate can be made adjustable.

[0031]FIGS. 4 and 5 shows schematically an decondensing device with a heating plate 4 placed in a distance over a cooling plate 5 leaving a space so that a test plate may be placed on the cooling plate 5 beneath the heating plate 4. The cooling and heating plates are held in distance of each other by a wall 18 comprising one or more small fans which can blow room temperature air over the cooling plate to keep it free from dew. The heating plate is heated by heaters build into the heating plate whereas the cooling plate 5 is cooled by a Peltier element 8 which are cooled by cooling ribs beneath the cooling plate. Legs 19 support the whole apparatus.

[0032] The reading of the test plates is performed automatically. The test plates made ready for reading may be stored I piles from which they are taken by a robot an carried to the decondenser apparatus in which they are inserted for a set time where after they are again taken by the robot and inserted in an imager, which automatically performs a reading of the light from the wells. 

1. Method for counteracting condense dew on a transparent cover film covering each well in an array of wells which forms a test plate having a lower side formed by the bottoms of the wells and an upper side formed by the upper edges of the wells onto which edges the cover film is sealingly attached, characterized in that the test plate for a set time is placed with its lower surface contacting a cooling plate which is kept at a set temperature below the room temperature and with its upper surface in a distance from a heating plate kept at a set temperature higher than the room temperature.
 2. Method according to claim 1 characterised in that the cooling plate is maintained in the temperature interval 0-10° C. and the heating plate is held in the temperature interval 50-110° C., preferably 60-75° C.
 3. Method according to claim 1 or 2, characterised in that the time the test plate stays between the cooling plate and the heating plate is 1-10 minutes, preferably 4-6 minutes.
 4. An apparatus for realising the method according to claim 1, characterised in that it comprises, a cooling plate on which a test plate can be placed, a heating plate parallel with the cooling plate in a distance from the cooling plate which distance is larger than the thickness of the test plate, cooling means maintaining the cooling plate at a set temperature lower than the room temperature, and heating means maintaining the heating plate at a set temperature over the room temperature.
 5. An apparatus according to claim 4 characterise din that the heating means comprises an electric resistive heating element and a heat distributing plate to obtain an even heating all over the heating surface facing the upper side of the test plate.
 6. An apparatus according to claim 4 or 5, characterised in that the cooling plate is cooled by a Peltier element.
 7. An apparatus according to any of the claims 4-6, characterised in that means are provided for setting the temperatures of the heating and the cooling plate, which means cooperating with feed back signals from the cooling and the heating plate controls a power supply so that set temperatures for the respective plates are maintained at a set values.
 8. An apparatus according to anyone of the claims 4-7 characterised in that the cooling plate is shaped with a raised platform mating a depression in the bottom of a test plate.
 9. An apparatus according to anyone of the claims 4-8 characterised in that fans are provided which blows room temperature air over the cooling plate to keep this plate dew free. 